Cu[(PPh3)2O](acac): Cu+ charge-compensated by a coordinating acac- anion

Article abstract of DOI:10.1016/j.inoche.2007.09.027

A complex Cu[(PPh₃)₂O](acac)[(PPh₃)₂O = Bis(2-diphenyl-phosphinophenyl) ether; acac = acetylacetone] was obtained by solution reactions and structurally characterized. The title complex is characterized by an isolated structure. X-ray structure analysis of the title complex shows that acac and (PPh₃)₂O behave as chelating ligands. Photoluminescent investigation reveals that the title complex displays a strong blue-light emission.

Full text of DOI:10.1016/j.inoche.2007.09.027

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Inorganic Chemistry Communications 10 (2007) 1561–1564
www.elsevier.com/locate/inoche
Cu[(PPh3)2O](acac): Cu+ charge-compensated by a
coordinating acacÀ anion
*
Yi-Ming Xie , Ji-Huai Wu
College of Materials Science and Engineering, Huaqiao University, Quanzhou, Fujian 362021, PR China
Received 22 August 2007; accepted 14 September 2007
Available online 6 October 2007
Abstract
A complex Cu[(PPh3)2O](acac)[(PPh3)2O = Bis(2-diphenyl-phosphinophenyl) ether; acac = acetylacetone] was obtained by solution
reactions and structurally characterized. The title complex is characterized by an isolated structure. X-ray structure analysis of the title
complex shows that acac and (PPh3)2O behave as chelating ligands. Photoluminescent investigation reveals that the title complex displays
a strong blue-light emission.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Copper; Crystal structure; Diketone; Photoluminescence
Copper(I) complexes containing phosphine ligands have
been the focus of much investigation in the last few years
because of the novel structural and reactive features of
these complexes. In light of this growing interest [1], many
examples of complexes containing phosphine ligands are
known with a variety of metals in different oxidation states
and stereochemistry [2]. Among these complexes, copper(I)
complexes are relatively rare [3] and copper(I) complexes
containing mixed phosphine and acac ligands have not
been documented thus far. To our best knowledge, among
the known copper(I) complexes containing acac ligand, the
charge of the Cu+ center is usually compensated by an iso-
lated anionic moiety, such as ClOÀ, F6PÀ, NOÀ and BrÀ,
of the Cu+ center is compensated by a coordinating anionic
moiety, i.e. acacÀ.
The title complex was obtained from the reaction of
copper powder, bis(2-diphenyl-phosphinophenyl) ether
and acac by solution reactions [6]. X-ray diffraction analy-
sis [7] reveals that the structure of the title complex consists
of discrete molecules. A view of the molecule, with the
numbering scheme, is depicted in Fig. 1. In the title com-
plex the copper(I) ion is tetrahedrally coordinated by two
phosphorus atoms from one (PPh3)2O ligand and two oxy-
gen atoms from one acac moiety. The Cu–P distances in
˚
Cu[(PPh3)2O](acac) are 2.2426(8) and 2.2666(8) A, with a
˚
mean value of 2.2546(8) A, comparable with the average
4
3
which does not coordinate to the Cu+ center [4] and the
examples of the Cu+ center charge-compensated by a coor-
dinating anionic moiety are very rare [5]. Herein we
describe the synthesis, structure and photoluminescence
of a complex Cu[(PPh3)2O](acac), which is the first example
of copper(I) complexes containing mixed phosphine and
acac ligands. Furthermore, in the title complex, the charge
value of 2.2312(8) A found in [Cu(PPh3)2(NO3)] [8]. The
˚
˚
observed Cu–Oacac distances of 2.056(2) and 2.044(2) A
are longer than those Cu–Oacac distances found in the cop-
per(I) complexes containing acac ligands, in which the cop-
per metals are coordinated by acac and other ligands, such
as acetic acid, phen, Me2bipy, NCS, and so on. [9]. This
may be caused by the fact that the coordination of
(PPh3)2O ligand to Cu lead to the weakening and lengthen-
ing of the Cu–Oacac bond. The bond lengths of the C–C
bonds in the phenyl rings are range from 1.357(5) to
*
Corresponding author.
˚
˚
1.405(4) A, with the average value of 1.3794(7) A. In acac
E-mail address: xym8790@yahoo.com.cn (Y.-M. Xie).
1387-7003/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2007.09.027

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Y.-M. Xie, J.-H. Wu / Inorganic Chemistry Communications 10 (2007) 1561–1564
moiety, the bond lengths of C(38)–C(39) and C(39)–C(40)
˚
being 1.389(5) and 1.394(5) A are shorter than those of sin-
gle bonds C(37)–C(38) and C(40)–C(41) being 1.525(5) and
˚
˚
1.522(5) A, but close to the average value of 1.3794(7) A of
the C–C bonds in the phenyl rings, indicating C(38), C(39)
and C(40) atoms form a conjugated system. The formation
of this conjugated system may be interpreted by the
following mechanism: before coordinating to the copper
center, the acac ligand rearranges as an enol-form and
then coordinates to the copper center with the formation
of the conjugated system, as shown in the Scheme 1. For
the title complex, there are weak intermolecular pÁ Á Áp
stacking interactions between the rings composed of atoms
C25–C30. The distance between the ring centroids is ca.
˚
3.74 A. There is no hydrogen bonding among the isolated
molecules. The weak intermolecular pÁ Á Áp stacking interac-
tions and the van de Waals’ force should contribute to the
stability of the crystal packing (Fig. 2).
Structural studies involving phosphine species of other
transition metals (Mn [10], Mo [11]) are less common
Fig. 1. ORTEP drawing of the title complex with 25% thermal ellipsoids.
Hydrogen atoms were omitted for clarity.
H2
C
H
H
H3C
CH3
rearrange
H3C
CH3
H3C
CH3
C
C
C
O
C
O
C
C
O
C
O
C
O
Cu+
+ H+
OH
Cu+
Scheme 1. The formation of the conjugated system.
Fig. 2. Packing diagram of the title complex with hydrogen atoms were omitted for clarity. The dashed lines represent pÁ Á Áp stacking interactions.

Y.-M. Xie, J.-H. Wu / Inorganic Chemistry Communications 10 (2007) 1561–1564
1563
but, in general, reveal linear P–M–P fragments and planar
M2P4 skeletal units. For d10 complexes, however, the
P–M–P units are distinctly non-linear [12]. X-ray structural
characterization of the title complex, clearly reveals that
the P–M–P angle [114.08(3)°] in the complex is not
restricted by steric crowding of (PPh3)2O phenyl rings, as
the cases found in the Refs. [3c,3d].
good photoluminescent property can be developed. Future
investigations in this field are in progress in our laboratory.
Acknowledgements
We gratefully acknowledge the financial support of the
NSF of China (50572030) and the NSF of Fujian Province
(2004HZ01-3).
To date, few copper(I) complexes containing acac ligand
have been reported. Moreover, in these complexes the
charge of the Cu+ center in one isolated moiety is usually
compensated by another isolated anionic moiety, such as
ClOÀ, F6PÀ, NOÀ and BrÀ, which does not coordinate to
Appendix A. Supplementary material
4
3
CCDC No. 648740 contains the supplementary crystal-
lographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif. Supple-
mentary data associated with this article can be found, in
the online version, at doi:10.1016/j.inoche.2007.09.027.
the Cu+ center [4] and, to our best knowledge, only one
complex in which the Cu+ center is charge-compensated
by a coordinating anionic moiety has been documented
[5]. In the title complex, however, the charge of the Cu+
center is compensated by a coordinating anionic moiety
– acacÀ. Therefore, the title complex is the first example
of which the Cu+ center is charge-compensated by a coor-
dinating acacÀ anion.
References
The solid-state emission spectrum of the title complex is
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of the title complex is given in Fig. 3. The photolumines-
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mum wavelength of 461 nm upon photo-excitation at
357 nm. The emission should probably be assigned to
metal-to-ligand charge transfers (MLCT). Thus, this com-
plex may be a candidate in blue-light luminescent
materials.
In brief, by using solution reactions of copper powder,
(PPh3)2O and acac, a new complex was obtained, which
is the first example in the complexes the Cu+ center being
charge-compensated by a coordinating acacÀ anion. This
complex exhibits a broad and strong photoluminescent
emission band, and it is a candidate of blue-light materials.
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ꢀ
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˚
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Y.-M. Xie, J.-H. Wu / Inorganic Chemistry Communications 10 (2007) 1561–1564
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